<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			*{
				margin: 0;
				padding: 0;
			}
			
			.ad{
				width:  100px;
				height: 100px;
				background: red;
				position: absolute;
				z-index: 10;
			}
			
			.cb{
				width:  200px;
				height: 150px;
				background: blue;
			}
		</style>
	</head>
	<body>
		<div class="ad">
			
		</div>
		<div class="cb">
			
		</div>
	</body>
</html>